As terminal technologies and image processing technologies advance, fingerprint recognition technology, as a high-security recognition technology, has been applied to many fields. The fingerprint recognition technology can bring security protection for individual private devices and is convenient for users. For example, terminals, application software or files of the terminal can be encrypted or decrypted (in other words, locked or unlocked) via the fingerprint recognition technology, to provide a better experience for the users.
The fingerprint recognition technology needs the user to touch a surface of a fingerprint sensor of the terminal with a finger, to acquire fingerprint information of the user. Inevitably, in a process of acquiring the fingerprint information of the user, water or other foreign materials (also known as a foreign object) may be present on the surface of the fingerprint sensor or the finger of the user. Methods for determining existence of a foreign material on a surface of a fingerprint sensor tend to be complicated without high accuracy.